The present invention relates to Rotating Compensator Sample System Investigation Systems and more particularly to use of Beam Splitting Analyzer means therein to simultaneously provide two electromagnetic beams, each thereof having a different effective Analyzer Azimuthal angle imposed thereupon. In use each of said two beams of electromagnetic radiation is directed to a separate detector such that two corresponding data sets are simultaneously, rather than sequentially as required where conventional Rotatable Analyzer means are utilized, obtained.
The practice of ellipsometry is well established as a non-destructive approach to determining characteristics of sample systems, and can be practiced in real time. The topic is well described in a number of publications, one such publication being a review paper by Collins, titled xe2x80x9cAutomatic Rotating Element Ellipsometers: Calibration, Operation and Real-Time Applicationsxe2x80x9d, Rev. Sci. Instrum., 61(8) (1990).
Continuing, in general, modern practice of ellipsometry typically involves causing a spectroscopic beam of electromagnetic radiation, in a known state of polarization, to interact with a sample system at at least one angle of incidence with respect to a normal to a surface thereof, in a plane of incidence. (Note, a plane of incidence contains both a normal to a surface of an investigated sample system and the locus of said beam of electromagnetic radiation). Changes in the polarization state of said beam of electromagnetic radiation which occur as a result of said interaction with said sample system are indicative of the structure and composition of said sample system. The practice of ellipsometry further involves proposing a mathematical model of the ellipsometer system and the sample system investigated by use thereof, and experimental data is then obtained by application of the ellipsometer system. This is typically followed by application of a square error reducing mathematical regression to the end that parameters in the mathematical model which characterize the sample system are evaluated, such that the obtained experimental data, and values calculated by use of the mathematical model, are essentially the same.
A typical goal in ellipsometry is to obtain, for each wavelength in, and angle of incidence of said beam of electromagnetic radiation caused to interact with a sample system, sample system characterizing PSI and DELTA values, (where PSI is related to a change in a ratio of magnitudes of orthogonal components rp/rs in said beam of electromagnetic radiation, and wherein DELTA is related to a phase shift entered between said orthogonal components rp and rs), caused by interaction with said sample system:
PSI=|rp/rs|;
and
DELTA=(xcex94rpxe2x88x92xcex94rs).
As alluded to, the practice of ellipsometry requires that a mathematical model be derived and provided for a sample system and for the ellipsometer system being applied. In that light it must be appreciated that an ellipsometer system which is applied to investigate a sample system is, generally, sequentially comprised of:
a. a Source of a beam electromagnetic radiation;
b. a Polarizer element;
c. optionally a compensator element;
d. (additional element(s));
e. a sample system;
f. (additional element(s));
g. optionally a compensator element;
h. an Analyzer element; and
i. a Spectroscopic Detector System.
Each of said components b.-i. must be accurately represented by a mathematical model of the ellipsometer system along with a vector which represents a beam of electromagnetic radiation provided from said source of a beam electromagnetic radiation, Identified in a. above)
Various conventional ellipsometer configurations provide that a Polarizer, Analyzer and/or Compensator(s) can be rotated during data acquisition, and are describe variously as Rotating Polarizer (RPE), Rotating Analyzer (RAE) and Rotating Compensator (RCE) Ellipsometer Systems. It is noted that nulling ellipsometers, in which elements therein are rotatable rather than rotating, and that ellipsometers containing modulation elements also are known.
Continuing, in use, data sets can be obtained with an ellipsometer system configured:
with a sample system present,
sequentially for cases where other sample systems are present, and
where the ellipsometer system is configured in a straight-through configuration wherein a beam of electromagnetic radiation is caused to pass straight through the ellipsometer system without interacting with a sample system.
Simultaneous mathematical regression utilizing multiple data sets can allow calibration of ellipsometers and evaluation of sample system characterizing PSI and DELTA values. The obtaining of numerous data sets with an ellipsometer system configured with, for instance, a sequence of sample systems present and/or wherein a sequential plurality of polarization and/or analyzer azimuthal angle states are imposed on an electromagnetic beam caused to interact with one or more sample systems, can allow system calibration of numerous ellipsometer system variables. It is noted, however, that it is often inconvenient to have to sequentially reconfigure an ellipsometer system to obtain multiple data sets. It is that problem to which the present invention provides an answer.
As it is relevant to the present invention it is noted at this point that polarizer and analyzer elements often comprise rotatable elements which serve to provide, or detect, a single beam of linearly polarized electromagnetic radiation, and that multiple data sets can correspond to multiple azimuthal angle rotation positions of said analyzer.
With the present invention in mind it is disclosed that relevant Patents include U.S. Pat. No. 5,872,630 to Johs et al., (said 630 Patent being incorporated by reference hereinto), which describes a Rotating Compensator Ellipsometer System. Said 630 Patent rotating compensator ellipsometer is described as being a sample system investigation system comprising a source of a beam of electromagnetic radiation, a polarizer, a stage for supporting a sample system, an analyzer, and a detector system, said rotating compensator sample system investigation system further comprises at least one compensator(s) positioned at a location selected from the group consisting of:
before said stage for supporting a sample system; and
after said stage for supporting a sample system; and
both before and after said stage for supporting a sample system;
such that when said rotating compensator sample system investigation system is used to investigate a sample system present on said stage for supporting a sample system, said polarizer means and analyzer means are maintained essentially fixed in position and at least one of said at least one compensator(s) is caused to continuously rotate while a beam of electromagnetic radiation produced by said source of a beam of electromagnetic radiation is caused to pass through said polarizer means and said at least one compensator(s), said beam of electromagnetic radiation being also caused to interact with said sample system and pass through said analyzer means and enter said detector system.
Further disclosed is a U.S. Pat. No. 5,416,588 to Ducharme which describes use of a Wollaston Prism as an Analyzer beam splitting means in said Modulation Element Ellipsometer System.
U.S. Pat. No. 5,946,098 to Johs et al. is disclosed as providing numerous designs for compensators which can be used in a present invention system. Said 098 Patent is incorporated by reference herewithin.
As the present invention includes regression calibration, a Patent to Thompson et al. U.S. Pat. No. 5,706,212 is also disclosed as it teaches a mathematical regression based double Fourier series ellipsometer calibration procedure for application, primarily, in calibrating ellipsometers system utilized in infrared wavelength range. Bi-refringent, transmissive window-like compensators are described as present in the system thereof, and discussion of correlation of retardations entered by sequentially adjacent elements which do not rotate with respect to one another during data acquisition is described therein. Said 212 Patent is incorporated by reference herewithin.
Also, while not citing the Johs paper, a Patent to Chen et al., U.S. Pat. No. 5,581,350, describes regression calibration of ellipsometer systems.
Patents which describe compensator systems for application in present invention systems are:
U.S. Pat. No. 5,963,325;
U.S. Pat. No. 5,946,098;
U.S. Pat. No. 6,084,674;
U.S. Pat. No. 6,084,675;
U.S. Pat. No. 6,100,981;
U.S. Pat. No. 6,118,537; and
U.S. Pat. No. 6,141,102.
U.S. Pat. No. 5,002,371 to Wright and Russian Patent No. SU 1432439 are also mentioned as they describe means for beam splitting.
A paper, which is incorporated by reference herewithin, is by Johs, and titled xe2x80x9cRegression Calibration Method for Rotating Element Ellipsometersxe2x80x9d, Thin Solid Films, 234 (1993). Said paper is disclosed as it describes a mathematical regression based approach to calibrating ellipsometer systems.
Further cited is a paper titled xe2x80x9cA Two-Channel Polarization Modulation Ellipsometerxe2x80x9d, Jellison and Modine, Appl. Opt., (October 1990).
Even in view of relevant prior art, there remains need for a more convenient approach to simultaneously providing multiple data sets in the context of rotating compensator material system investigation systems. The present invention responds to said identified needs.
The 630 Patent to Johs et al. cited in the Background Section of this Specification describes, in the context of a Rotating Compensator Sample System Investigation System, describes the presence of Rotatable Polarizer and Analyzer elements which can be set to various static positions during data acquisition, during which data acquisition at least one present Compensator is caused to rotate. To calibrate said system it is typically required that two data sets be obtained, which data sets can correspond to two azimuthal angle settings of the Analyzer and/or Polarizer element.
The present invention rotating compensator sample system investigation system comprises a source of a beam of electromagnetic radiation, a polarizer, a stage for supporting a sample system, a beam splitting analyzer means, and at least two detector systems, each said detector system being positioned to separately intercept one of at least two beams which emerge from said beam splitting analyzer means; said rotating compensator sample system investigation system further comprising at least one compensator(s) positioned at a location selected from the group consisting of:
before said stage for supporting a sample system; and
after said stage for supporting a sample system; and
both before and after said stage for supporting a sample system.
It is specifically noted that the present invention rotating compensator sample system Investigation system differs from that disclosed in the 630 Patent, (and from all other known similar Rotating Compensator based systems), in that in place of a Rotatable Analyzer and a Single Detector, (typically comprising multiple detector elements), there is present:
a beam splitting analyzer means, and at least two detector systems, each said detector system being positioned to separately intercept one of at least two beams of electromagnetic radiation which emerge from said beam splitting analyzer means . . .
In use, when said present invention rotating compensator sample system investigation system is used to investigate a sample system present on said stage for supporting a sample system, said polarizer means and beam splitting analyzer means are maintained essentially fixed in position and at least one of said at least one compensator(s) is caused to continuously rotate while a beam of electromagnetic radiation produced by said source of a beam of electromagnetic radiation is caused to pass through said polarizer means and said at least one compensator(s), said beam of electromagnetic radiation being also caused to interact with said sample system and pass through said beam splitting analyzer means such that two beams of electromagnetic radiation, (eg. affected to correspond to two azimuthal positions of a conventional analyzer means), are simultaneously caused to each separately enter different of said at least two detector systems.
A method of calibrating a rotating compensator sample system investigation system while extracting sample system PSI and DELTA values, comprising the steps of:
a. providing a rotating compensator sample system investigation system as described above; in either order practicing steps b. and steps (c. and d.):
b. developing a mathematical model of said rotating compensator sample system investigation system which comprises as calibration parameter variables polarizer azimuthal angle orientation, present sample system PSI, present sample system DELTA, compensator azimuthal angle orientation(s), matrix components of said at least one compensator(s), and effective beam splitting analyzer means azimuthal angle orientations, which mathematical model is effectively a transfer function which enables calculation of electromagnetic beam intensity as a function of wavelength detected by a detector when given intensity as a function of wavelength provided by said source of a beam of electromagnetic radiation;
c. causing a beam of electromagnetic radiation produced by said source of a beam of electromagnetic radiation, to pass through said polarizer, interact with a sample system caused to be in the path thereof, pass through said beam splitting analyzer means such that at least two beams emerge therefrom with each thereof entering a different one of said at least two detector systems; said beam of electromagnetic radiation also being caused to pass through said compensator(s) positioned at a location selected from the group consisting of:
before said stage for supporting a sample system;
after said stage for supporting a sample system; and
both before and after said stage for supporting a sample system;
d. simultaneously obtaining two data sets of intensity values, corresponding to the effective azimuthal angles of two beams of electromagnetic radiation exiting said beam splitting analyzer means over time, while at least one of said at least one compensator(s) is caused to continuously rotate;
e. performing a mathematical regression of said mathematical model onto said at least two data sets;
said regression based calibration procedure serving to compensate said mathematical model for azimuthal angles of said polarizer, said at least one compensator(s), matrix elements of said at least one compensator(s), and said two effective analyzer angles, in addition evaluating the PSI and DELTA of the present sample system.
Said method of calibrating a rotating compensator sample system investigation system can further comprise, in the step d. simultaneously obtaining two data sets of intensity values vs. effective azimuthal angles of said beam splitting analyzer means for each of two sample systems; and in step e. including simultaneous regression onto data for both sample systems.
Finally, as the present invention comprises a rotating compensator, it is noted that any functional compensator can be utilized, however, for reference, a catalog of suitable Compensators, (many Patented by the J. A. Woollam Co.), are recited directly. Compensators disclosed in co-pending patent application Ser. No. 09/496,011 are:
a single element compensator;
a compensator system comprised of at least two per se. zero-order waveplates (MOA) and (MOB), said per se. zero-order waveplates (MOA) and (MOB) having their respective fast axes rotated to a position offset from zero or ninety degrees with respect to one another, with a nominal value being forty-five degrees;
a compensator system comprised of a combination of at least a first (ZO1) and a second (ZO2) effective zero-order wave plate, said first (ZO1) effective zero-order wave plate being comprised of two multiple order waveplates (MOA1) and (MOB1) which are combined with the fast axes thereof oriented at a nominal ninety degrees to one another, and said second (ZO2) effective zero-order wave plate being comprised of two multiple order waveplates (MOA2) and (MOB2) which are combined with the fast axes thereof oriented at a nominal ninety degrees to one another; the fast axes (FAA2) and (FAB2) of the multiple order waveplates (MOA2) and (MOB2) in said second effective zero-order wave plate (ZO2) being rotated to a position at a nominal forty-five degrees to the fast axes (FAA1) and (FAB1), respectively, of the multiple order waveplates (MOA1) and (MOB1) in said first effective zero-order waveplate (ZO1);
a compensator system comprised of a combination of at least a first (ZO1) and a second (ZO2) effective zero-order wave plate, said first (ZO1) effective zero-order wave plate being comprised of two multiple order waveplates (MOA1) and (MOB1) which are combined with the fast axes thereof oriented at a nominal ninety degrees to one another, and said second (ZO2) effective zero-order wave plate being comprised of two multiple order waveplates (MOA2) and (MOB2) which are combined with the fast axes thereof oriented at a nominal ninety degrees to one another; the fast axes (FAA2) and (FAB2) of the multiple order waveplates (MOA2) and (MOB2) in said second effective zero-order wave plate (ZO2) being rotated to a position away from zero or ninety degrees with respect to the fast axes (FAA1) and (FAB1), respectively, of the multiple order waveplates (MOA1) and (MOB1) in said first effective zero-order waveplate (ZO1);
a compensator system comprised of at least one zero-order waveplate, ((MOA) or (MOB)), and at least one effective zero-order waveplate, ((ZO2) or (ZO1) respectively), said effective zero-order wave plate, ((ZO2) or (ZO1)), being comprised of two multiple order waveplates which are combined with the fast axes thereof oriented at a nominal ninety degrees to one another, the fast axes of the multiple order waveplates in said effective zero-order wave plate, ((ZO2) or (ZO1)), being rotated to a position away from zero or ninety degrees with respect to the fast axis of the zero-order waveplate, ((MOA) or (MOB)).
Additional compensator systems, previously disclosed in patent application Ser. No. 08/997,311, (now U.S. Pat. No. 5,946,098 which is incorporated herewithin), and CIP""s therefrom, which compensators are specifically within the scope of application with the present invention are:
a compensator system comprised of a first triangular shaped element, which as viewed in side elevation presents with first and second sides which project to the left and right and downward from an upper point, which first triangular shaped element first and second sides have reflective outer surfaces; said retarder system further comprising a second triangular shaped element which as viewed in side elevation presents with first and second sides which project to the left and right and downward from an upper point, said second triangular shaped element being made of material which provides reflective interfaces on first and second sides inside thereof; said second triangular shaped element being oriented with respect to the first triangular shaped element such that the upper point of said second triangular shaped element is oriented essentially vertically directly above the upper point of said first triangular shaped element; such that in use an input electromagnetic beam of radiation caused to approach one of said first and second sides of said first triangular shaped element along an essentially horizontally oriented locus, is caused to externally reflect from an outer surface thereof and travel along a locus which is essentially upwardly vertically oriented, then enter said second triangular shaped element and essentially totally internally reflect from one of said first and second sides thereof, then proceed along an essentially horizontal locus and essentially totally internally reflect from the other of said first and second sides and proceed along an essentially downward vertically oriented locus, then externally reflect from the other of said first and second sides of said first triangular shaped elements and proceed along an essentially horizontally oriented locus which is undeviated and undisplaced from the essentially horizontally oriented locus of said input beam of essentially horizontally oriented electromagnetic radiation even when said retarder is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation;
a compensator system comprised of, as viewed in upright side elevation, first and second orientation adjustable mirrored elements which each have reflective surfaces; said compensator/retarder system further comprising a third element which, as viewed in upright side elevation, presents with first and second sides which project to the left and right and downward from an upper point, said third element being made of material which provides reflective interfaces on first and second sides inside thereof; said third element being oriented with respect to said first and second orientation adjustable mirrored elements such that in use an input electromagnetic beam of radiation caused to approach one of said first and second orientation adjustable mirrored elements along an essentially horizontally oriented locus, is caused to externally reflect therefrom and travel along a locus which is essentially upwardly vertically oriented, then enter said third element and essentially totally internally reflect from one of said first and second sides thereof, then proceed along an essentially horizontal locus and essentially totally internally reflect from the other of said first and second sides and proceed along an essentially downward vertically oriented locus, then reflect from the other of said first and second orientation adjustable mirrored elements and proceed along an essentially horizontally oriented propagation direction locus which is essentially undeviated and undisplaced from the essentially horizontally oriented propagation direction locus of said input beam of essentially horizontally oriented electromagnetic radiation even when said compensator/retarder is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation;
a compensator system comprised of a parallelogram shaped element which, as viewed in side elevation, has top and bottom sides parallel to one another, both said top and bottom sides being oriented essentially horizontally, said retarder system also having right and left sides parallel to one another, both said right and left sides being oriented at an angle to horizontal, said retarder being made of a material with an index of refraction greater than that of a surrounding ambient; such that in use an input beam of electromagnetic radiation caused to enter a side of said retarder selected from the group consisting of: (right and left), along an essentially horizontally oriented locus, is caused to diffracted inside said retarder system and follow a locus which causes it to essentially totally internally reflect from internal interfaces of both said top and bottom sides, and emerge from said retarder system from a side selected from the group consisting of (left and right respectively), along an essentially horizontally oriented locus which is undeviated and undisplaced from the essentially horizontally oriented locus of said input beam of essentially horizontally oriented electromagnetic radiation even when said retarder is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation;
a compensator system comprised of first and second triangular shaped elements, said first triangular shaped element, as viewed in side elevation, presenting with first and second sides which project to the left and right and downward from an upper point, said first triangular shaped element further comprising a third side which is oriented essentially horizontally and which is continuous with, and present below said first and second sides; and said second triangular shaped element, as viewed in side elevation, presenting with first and second sides which project to the left and right and upward from an upper point, said second triangular shaped element further comprising a third side which is oriented essentially horizontally and which is continuous with, and present above said first and second sides; said first and second triangular shaped elements being positioned so that a rightmost side of one of said first and second triangular shaped elements is in contact with a leftmost side of the other of said first and second triangular shaped elements over at least a portion of the lengths thereof; said first and second triangular shaped elements each being made of material with an index of refraction greater than that of a surrounding ambient; such that in use an input beam of electromagnetic radiation caused to enter a side of a triangular shaped element selected from the group consisting of: (first and second), not in contact with said other triangular shape element, is caused to diffracted inside said retarder and follow a locus which causes it to essentially totally internally reflect from internal interfaces of said third sides of each of said first and second triangular shaped elements, and emerge from a side of said triangular shaped element selected from the group consisting of: (second and first), not in contact with said other triangular shape element, along an essentially horizontally oriented locus which is undeviated and undisplaced from the essentially horizontally oriented locus of said input beam of essentially horizontally oriented electromagnetic radiation even when said retarder is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation;
a compensator system comprised of a triangular shaped element, which as viewed in side elevation presents with first and second sides which project to the left and right and downward from an upper point, said retarder system further comprising a third side which is oriented essentially horizontally and which is continuous with, and present below said first and second sides; said retarder system being made of a material with an index of refraction greater than that of a surrounding ambient; such that in use a an input beam of electromagnetic radiation caused to enter a side of said retarder system selected from the group consisting of: (first and second), along an essentially horizontally oriented locus, is caused to diffracted inside said retarder system and follow a locus which causes it to essentially totally internally reflect from internal interface of said third sides, and emerge from said retarder from a side selected from the group consisting of (second and first respectively), along an essentially horizontally oriented locus which is undeviated and undisplaced from the essentially horizontally oriented locus of said input beam of essentially horizontally oriented electromagnetic radiation even when said retarder system is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation; and
a compensator system comprised of first and second Berek-type retarders which each have an optical axes essentially perpendicular to a surface thereof, each of which first and second Berek-type retarders has a fast axis, said fast axes in said first and second Berek-type retarders being oriented in an orientation selected from the group consisting of: (parallel to one another and other than parallel to one another); said first and second Berek-type retarders each presenting with first and second essentially parallel sides, and said first and second Berek-type retarders being oriented, as viewed in side elevation, with first and second sides of one Berek-type retarder being oriented other than parallel to first and second sides of the other Berek-type retarder; such that in use an incident beam of electromagnetic radiation is caused to impinge upon one of said first and second Berek-type retarders on one side thereof, partially transmit therethrough then impinge upon the second Berek-type retarder, on one side thereof, and partially transmit therethrough such that a polarized beam of electromagnetic radiation passing through both of said first and second Berek-type retarders emerges from the second thereof in a polarized state with a phase angle between orthogonal components therein which is different than that in the incident beam of electromagnetic radiation, and in a propagation direction which is essentially undeviated and undisplaced from the incident beam of electromagnetic radiation even when said retarder system is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation;
a compensator system comprised of first and second Berek-type retarders which each have an optical axes essentially perpendicular to a surface thereof, each of which first and second Berek-type retarders has a fast axis, said fast axes in said first and second Berek-type retarders being oriented other than parallel to one another; said first and second Berek-type retarders each presenting with first and second essentially parallel sides, and said first and second Berek-type retarders being oriented, as viewed in side elevation, with first and second sides of one Berek-type retarder being oriented other than parallel to first and second sides of the other Berek-type retarder; such that in use an incident beam of electromagnetic radiation is caused to impinge upon one of said first and second Berek-type retarders on one side thereof, partially transmit therethrough then impinge upon the second Berek-type retarder, on one side thereof, and partially transmit therethrough such that a polarized beam of electromagnetic radiation passing through both of said first and second Berek-type retarders emerges from the second thereof in a polarized state with a phase angle between orthogonal components therein which is different than that in the incident beam of electromagnetic radiation, and in a propagation direction which is essentially undeviated and undisplaced from the incident beam of electromagnetic radiation, said compensator system further comprising third and forth Berek-type retarders which each have an optical axes essentially perpendicular to a surface thereof, each of which third and forth Berek-type retarders has a fast axis, said fast axes in said third and forth Berek-type retarders being oriented other than parallel to one another, said third and forth Berek-type retarders each presenting with first and second essentially parallel sides, and said third and forth Berek-type retarders being oriented, as viewed in side elevation, with first and second sides of one of said third and forth Berek-type retarders being oriented other than parallel to first and second sides of said forth Berek-type retarder; such that in use an incident beam of electromagnetic radiation exiting said second Berek-type retarder is caused to impinge upon said third Berek-type retarder on one side thereof, partially transmit therethrough then impinge upon said forth Berek-type retarder on one side thereof, and partially transmit therethrough such that a polarized beam of electromagnetic radiation passing through said first, second, third and forth Berek-type retarders emerges from the forth thereof in a polarized state with a phase angle between orthogonal components therein which is different than that in the incident beam of electromagnetic radiation caused to impinge upon the first side of said first Berek-type retarder, and in a direction which is essentially undeviated and undisplaced from said incident beam of electromagnetic radiation even when said retarder system is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation;
a compensator system comprised of first, second, third and forth Berek-type retarders which each have an optical axes essentially perpendicular to a surface thereof, each of which first and second Berek-type retarders has a fast axis, said fast axes in said first and second Berek-type retarders being oriented essentially parallel to one another; said first and second Berek-type retarders each presenting with first and second essentially parallel sides, and said first and second Berek-type retarders being oriented, as viewed in side elevation, with first and second sides of one Berek-type retarder being oriented other than parallel to first and second sides of the other Berek-type retarder; such that in use an incident beam of electromagnetic radiation is caused to impinge upon one of said first and second Berek-type retarders on one side thereof, partially transmit therethrough then impinge upon the second Berek-type retarder, on one side thereof, and partially transmit therethrough such that a polarized beam of electromagnetic radiation passing through both of said first and second Berek-type retarders emerges from the second thereof in a polarized state with a phase angle between orthogonal components therein which is different than that in the incident beam of electromagnetic radiation, and in a propagation direction which is essentially undeviated and undisplaced from the incident beam of electromagnetic radiation; each of which third and forth Berek-type retarders has a fast axis, said fast axes in said third and forth Berek-type retarders being oriented essentially parallel to one another but other than parallel to the fast axes of said first and second Berek-type retarders, said third and forth Berek-type retarders each presenting with first and second essentially parallel sides, and said third and forth Berek-type retarders being oriented, as viewed in side elevation, with first and second sides of one of said third and forth Berek-type retarders being oriented other than parallel to first and second sides of said forth Berek-type retarder; such that in use an incident beam of electromagnetic radiation exiting said second Berek-type retarder is caused to impinge upon said third Berek-type retarder on one side thereof, partially transmit therethrough then impinge upon said forth Berek-type retarder on one side thereof, and partially transmit therethrough such that a polarized beam of electromagnetic radiation passing through said first, second, third and forth Berek-type retarders emerges from the forth thereof in a polarized state with a phase angle between orthogonal components therein which is different than that in the incident beam of electromagnetic radiation caused to impinge upon the first side of said first Berek-type retarder, and in a direction which is essentially undeviated and undisplaced from said incident beam of electromagnetic radiation even when said retarder system is caused to rotate; with a result being that retardation is entered between orthogonal components of said input electromagnetic beam of radiation.
The present invention will be better understood by reference to the Detailed Description Section of this Specification, in conjunction with the Drawings.
It is therefore a primary objective and/or purpose of the present invention to teach a rotating compensator sample system investigation system which comprises a source of a beam of electromagnetic radiation, a polarizer, a stage for supporting a sample system, a beam splitting analyzer means, and two detector systems, each said detector system being positioned to separately intercept one of at least two beams which emerges from said beam splitting analyzer means; said rotating compensator sample system investigation system further comprising at least one compensator(s).
It is another objective and/or purpose of the present invention to teach regression based calibration and extraction of sample system PSI and DELTA values.
Other objectives and/or purposes of the present invention will become apparent by a reading of the Specification and Claims.